JP2015101791A - Hydrogen preparation method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen preparation method and hydrogen production apparatus as well as a corresponding computer program product, in which the hydrogen can be dried before compression.SOLUTION: Provided is a hydrogen preparation method in which a step of forming hydrogen that can be formed by involving external species in the suction side of an electrochemical compressor, and a step of transporting ions of hydrogen through the membrane of compressor by using the electrical potential applied between a first electrode on the suction side of compressor and a second electrode on the pressure side of compressor in order to enhance the hydrogen partial pressure in the pressure side of compressor and in order to hold the external species in the suction side of compressor, are carried out.

Description

  The present invention relates to a hydrogen preparation method, a hydrogen preparation apparatus and a corresponding computer program product.

  When hydrogen is produced by electrolysis of water, this hydrogen contains a water component in the form of water vapor generated in the process. In order to use hydrogen elsewhere, a preparation is made to remove water vapor from the hydrogen.

  DE 3650465T2 discloses a permeable polymer membrane for gas drying.

DE3650465T2

  In light of such background art, the present invention proposes an approach of a hydrogen preparation method, a hydrogen preparation apparatus, and a corresponding computer program product described in the superordinate concept of each independent claim. Advantageous embodiments result from the respective dependent claims and the following description.

  In order to accumulate hydrogen technically, compression of hydrogen is necessary. The compression can be performed mechanically by a compressor. However, in a mechanical compressor and a pressure tank, water in any form of liquid phase, solid phase, and gas phase can be an obstacle. This requires that the hydrogen be dried before mechanical compression.

  The above-described problems are the steps of generating hydrogen that can be generated by involving external species on the suction side of the electrochemical compressor, increasing the hydrogen partial pressure on the pressure side of the compressor, and the suction side of the compressor In order to retain the external species, hydrogen ions are passed through the compressor membrane using the electrical potential between the first electrode on the suction side of the compressor and the second electrode on the pressure side of the compressor. And the step of transporting the solution.

  In addition, the above problem is that an electrochemical compressor including a membrane, a first electrode on the suction side, and a second electrode on the pressure side, and hydrogen can be generated on the suction side of the compressor by involving external species. In the compressor, an electric potential is formed between the first electrode and the second electrode in order to increase the hydrogen partial pressure on the pressure side and retain external species on the suction side. This is solved by a hydrogen preparation device in which hydrogen ions are transported from the suction side of the compressor to the pressure side of the compressor.

  The method and apparatus embodiments of the present invention can solve the problems underlying the present invention quickly and effectively.

It is a block diagram of the hydrogen preparation apparatus by the Example of this invention. It is a schematic diagram of the hydrogen preparation method by the Example of this invention using the electrochemical compressor which combined the gas drying unit and compression unit of the electrolysis system. 3 is a flowchart of a method for preparing hydrogen according to an embodiment of the present invention.

  In the present invention, hydrogen is electrochemically compressed. In this case, hydrogen is transported through the membrane (membrane) in the form of ions. For this purpose, hydrogen is decomposed into ions and electrons by the catalyst on the suction side of the membrane. Electrons are pulled apart by the electrical potential. Ions stray through the membrane. Electrons are generated again on the pressure side of the membrane due to the electric potential, and these electrons and ions are recombined through catalytic action to generate hydrogen. Based on the formed electric potential, the equilibrium between the ions on the suction side and the ions on the pressure side shifts toward the pressure side. On the other hand, on the other hand, many ions stray from the suction side to the pressure side due to the electric potential.

  Since only hydrogen ions are transported through the membrane, water vapor remains on the suction side. The water vapor condenses on the membrane and wets it to improve its function.

  Electrochemical compressors have high efficiency, which is reduced only by resistance losses. Hydrogen is hardly heated during compression. Since the electrochemical compressor has no moving elements, little friction is generated. Similarly, the electrochemical compressor is quiet and does not vibrate.

  It should be understood that preparation means changing properties. In this case, the characteristics are changed according to the set requirements. In particular, the pressure and purity of hydrogen are adapted. The external species is particularly water. The water may be in the gas phase or vapor. The external species may be another gas different from hydrogen. The suction side is the side where the device performs suction, and the pressure side is the side where the device discharges. The suction side electrode and the pressure side electrode can be arranged directly on the membrane. However, the membrane must be electrically isolated. The membrane is configured to have a catalytic action. The membrane must be permeable to hydrogen ions.

  Hydrogen is generated using electrical energy. In this case, water is decomposed into hydrogen and oxygen. The external species is in particular water vapor. Direct bonding in one unit allows hydrogen to be produced and compressed in a tight space. Overall, the complexity of the device is greatly reduced since electrolysis and preparation are integrated into one system.

Hydrogen is transported to the pressure side at a set pressure. Alternatively or in addition, hydrogen may be transported to the pressure side at a set temperature or a set purity. In the automotive field, for example, pressures in the range of 30 bar to 800 bar and room temperature are conceivable. The hydrogen should advantageously have a purity of 5.0 H ₂ (corresponding to 99.999% H ₂ ). The suction side pressure can be set by the electric potential. After the hydrogen is transported through the membrane, it is cooled or heated to achieve the desired properties. With such a preparation, hydrogen can meet the set criteria.

  In the transport step, a predetermined DC voltage can be applied to the electrodes. The DC voltage can be smoothed. Hydrogen can be transported evenly by the DC voltage.

  Ions are transported quasi-isothermally through the membrane. In this case, the ions are transported with little heating. Note that the transportation can be performed with high efficiency even without heating.

  The method of the present invention further includes accumulating hydrogen in the pressure accumulator on the pressure side. A large amount of hydrogen can be accumulated in the pressure accumulator or pressure tank.

  The generator can be configured as an electrolyzer configured to decompose water into hydrogen and oxygen using electrical energy, and in particular to use an external species that is water vapor. The generator is connected in series with an electrochemical compressor in electrical terms and in hydrogen flow technology. The amount of hydrogen generated is proportional to the amount of energy used for electrolysis. The amount of hydrogen transported through the membrane is proportional to the amount of energy used for transport. Thus, electrolysis is closely related to transportation from an electrical perspective.

  The compressor may include at least one other membrane having another first electrode on the suction side and another second electrode on the pressure side. The other membrane and the membrane are arranged so as to follow each other and to gradually increase the hydrogen partial pressure from the suction side to the pressure side. Multiple membranes connected in series allow hydrogen to be generated at higher pressures. Similarly, a reduced pressure gradient can be set between the suction side and the pressure side of the membrane. In the latter case, individual membranes can be made thin, and hydrogen can be transported more dynamically.

  The membrane can be configured as a polymer electrolyte membrane. The polymer electrolyte membrane can be produced with a particularly uniform thickness.

  The membrane can have a discharge for discharging external species. By the said discharge part, the condensed water is discharged | emitted from a membrane. Thereby, the active area of a membrane can be maintained large.

  The apparatus of the present invention further comprises a pressure accumulator for accumulating hydrogen on the pressure side. With the pressure accumulator, the device of the present invention can be realized as a complete system.

  Advantageously, a computer program product can be constructed that includes program code stored on a machine-readable carrier. The machine readable carrier may be, for example, a semiconductor memory or a hard disk memory or an optical memory. The program code executes the method according to the above-described embodiments when the program product is executed on a computer or a predetermined device.

  The approach of the present invention will be described in detail below with reference to the illustrated embodiment.

  An advantageous embodiment of the invention is illustrated and described below. In the drawings, the same elements or elements having similar functions are denoted by the same reference numerals, and repeated description is omitted.

  An electrolysis system usually consists of a water generator, a (direct current) voltage source, an electrolysis layer stack, a gas scrubber and / or a gas dryer, a compressor and a (high pressure) gas accumulator.

  For gas drying, a condensation process (gas chiller) and a zeolite-based adsorption filter or pressure fluctuation adsorption part PSA (pressure swing adsorption) can be used. In this case, since the dew point at 1 bar is −60 ° C., if a pure condensation process occurs, the required gas quality cannot be obtained at pressures as low as 30 bar. The adsorption filter is significant only in a system with a small production volume, and also needs to be replaced for the regeneration of the adsorbent, thereby reducing the density of the system. Conversely, PSA is only significant in large scale systems, and requires reactor chamber regeneration to clean the process chamber, resulting in a large loss of 10% to 30% of the gas produced.

  A mechanical compressor can be used for the compression. In this case, an unlubricated compressor is used in order to avoid contamination of the hydrogen by the lubricating oil, but this has a short service life and / or maintenance intervals. Similarly, an ion compressor having a long lifetime can be used. However, the ion compressor requires a very large space.

The saturated content of water in the gas depends directly on the gas temperature and the gas pressure. As the pressure increases, the dew point for the set water vapor concentration also increases. The dew point at 99.999% H ₂ , the hydrogen quality normally required in the fuel cell field, is about 4 ° C. at 800 bar. This means that the required gas quality is achieved upon gas compression up to 800 bar and above and possibly subsequent gas cooling. Here, in the electrochemical compressor proposed in the present invention, residual moisture in hydrogen does not destroy the compressor, and conversely contributes to maintaining or increasing the proton conductivity of the membrane. Have advantages.

  The action of reducing water vapor in hydrogen by increasing the pressure is utilized in the electrochemical compressor proposed in the present invention. This is done by compressing the gas in one or more stages to the required pressure to achieve the required purity directly without additional gas drying.

The following table shows the dew point from 5.0 H ₂ water to ice.
_{P i P abs @ 0.01% H} 2 O T_sat
[Bar] [bar] [° C]
0.00001 1-60
0.0001 10 -42
0.001 100 -20
0.008 800 +4
0.01 1000 +7

  FIG. 1 shows a block diagram of an apparatus 100 for preparing hydrogen 102 according to an embodiment of the present invention. The preparation device 100 includes an electrochemical compressor 104 and a generation device 106. The electrochemical compressor 104 includes a membrane 108, a first electrode 110 on the suction side, and a second electrode 112 on the pressure side. An electrical potential is formed between the first electrode 110 and the second electrode 112 and the ions 114 of the hydrogen 102 are transported from the suction side 116 of the compressor 104 to the pressure side 118, thereby causing a pressure on the pressure side 118. The hydrogen partial pressure is increased and the external species 120 remains on the suction side 116. The generator 106 is configured to generate the hydrogen 102 on the suction side 116. Hydrogen 102 is generated by the participation of external species 120.

  In an advantageous configuration of the invention, the compressor 104 comprises at least one further membrane having another first electrode on the suction side and another second electrode on the pressure side. The other membrane and the membrane are arranged so that they are in phase with each other and the hydrogen partial pressure is gradually increased from the suction side toward the pressure side. Between each membrane 108 is a chamber for hydrogen that passes through one membrane and is transported to the next.

  In an advantageous configuration, each membrane 108 is configured as a polymer electrolyte membrane 108.

  In an advantageous configuration, each membrane 108 has a discharge for discharging external species. The discharge unit is arranged on the suction side and configured to discharge the external species 120 from the preparation apparatus 100.

  In an advantageous configuration, the electrochemical compressor 104 is directly supplied with hydrogen 102 from the electrolysis layer stack 106 without a pre-connected gas drying section. On the output side of the electrochemical compressor 104, the hydrogen 102 directly meets the requirements of the downstream system, such as a gas accumulator or fuel cell, depending on the pressure stage selected. The required gas dryness is improved by additional moderate gas cooling.

In an advantageous embodiment, the electrolysis layer stack 106 is operated directly in a differential pressure mode. Thereby, H ₂ production, drying and compression are performed in one element.

  Each membrane 108 of the electrochemical cell 104 does not require an additional water supply. This is because the water supply is guaranteed by the residual moisture 120 of the hydrogen 102.

  In an advantageous configuration, the drainage can be integrated into the membrane 108.

  In an advantageous configuration, the target pressure is achieved in one stage.

  In another advantageous configuration, the target pressure is achieved by a plurality of pressure stages, i.e. by connecting a plurality of electrochemical cells 104 in series. In this case, technically, compression of hydrogen 102 from 1 bar to 1000 bar is possible.

FIG. 2 shows a schematic diagram of a method for preparing hydrogen H ₂ (102) according to an example of the present invention. The method here is performed in the electrolysis system 200 using an electrochemical compressor 104 as an apparatus combining a gas drying unit and a compression unit. Here, the generator 106 is an electrolyzer or electric device configured to utilize the electrical energy 202 to decompose water H ₂ O (204) into hydrogen H ₂ (102) and oxygen O ₂ (206). This is a decomposition layer stack 106. Here, the hydrogen H ₂ O generated in the process is added to the hydrogen H ₂ (102) as the external species 120. The compressed and washed hydrogen H ₂ (102) is accumulated in the pressure accumulator 208 on the pressure side. Here, the electrical energy 202 is formed as a DC voltage.

  The approach of the present invention eliminates a separate gas drying section that is pre-connected to the compressor that was essential in the mechanical system. For this reason, the complexity of the system can be greatly reduced. Thereby, in the electrolysis system 200 of the present invention, both the structural space and the noise level are reduced and the maintenance interval is increased as compared with the mechanical system.

  In other words, FIG. 2 shows an electrolysis system 200 with an electrochemical cell 104 that compresses and drys hydrogen 102.

The electrolysis layer stack 106 or electrolysis system 200 for hydrogen produces hydrogen from the water 204 and the gas stream 202, which is applied, for example, in a hydrogen tank facility for the fuel cell vehicle or power to gas sector. Here, fuel cell vehicles place particularly high demands on the purity of the hydrogen 102 produced, ie the hydrogen content. Usually, a purity of 5.0H ₂ (99.999% H ₂ ) is required. One reason is the contamination sensitivity of the fuel cell catalyst, and the other is the condensation of the water 120 under low temperature and / or high pressure. These can cause pressure fluctuations in the gas supply or freezing of the pipelines.

  Gas drying of the hydrogen 102 produced by electrolysis is essential. This is because the hydrogen 102 has a predetermined moisture 120 generated by the process on the output side of the electrolysis layer stack 106. Such moisture 120 may cause water hammer during compression with the mechanical compressor and damage the mechanical compressor.

  In the approach of the present invention, the compression of hydrogen 102 is performed in an electrochemical cell 104 as an electrochemical compressor. Unlike the mechanical compressor, the electrochemical compressor 104 performs moisture management at the same time as the compression of the hydrogen 102, so that it is not necessary to connect an additional gas drying section in advance. Thus, the complexity of the system is greatly reduced.

  The main advantage of the approach of the present invention is that the use of electrochemical compressor 104 eliminates the need for additional elements for gas drying and reduces system complexity. This particularly saves space for the entire system 200 and also improves system efficiency.

  Since the gas 102 can be compressed without moving elements, the noise of operation of the system 200 is reduced and the number of maintenance is reduced.

For the compression of the hydrogen 102, an electrochemical compressor 104, for example a compressor based on a polymer electrolyte membrane PEM, is used. By applying a DC voltage 204 to the electrode of the electrochemical cell 104, an H ⁺ flow from one side of the membrane to the other occurs, causing a pressure increase. In this case, the pressure increase achieved depends on the applied voltage.
U = RT / 2FIn (p ₂ / p ₁ ) + ir + η
Where U is the applied voltage, R is the gas constant, T is the temperature, F is the Faraday constant, p ₁ is the pressure in the first gas space, and p ₂ is the second It is the pressure in the gas space, i is the current density, r is the resistance of the electrochemical cell 104, and η is the overvoltage.

  In this case, the efficiency of electrochemical compression is very good, especially compared to adiabatic compression with a mechanical compressor, since the compression of the gas 102 is performed quasi-isothermally.

  FIG. 3 shows a flow chart of a method 300 for preparing hydrogen according to an embodiment of the present invention. The preparation method 300 includes a generation step 302 and a transport step 304. In the generation step 302, hydrogen is generated on the suction side of the electrochemical compressor. Here, the pure form of hydrogen is produced with the participation of external species. In the transport step 304, hydrogen ions are transported through the compressor membrane by an electrical potential. The electric potential is formed between the first electrode on the suction side of the compressor and the second electrode on the pressure side. Transport increases the hydrogen partial pressure on the pressure side of the compressor. External species remain on the suction side of the compressor.

  In an advantageous configuration, in the generation step 302, hydrogen is generated using electrical energy. For this, water is broken down into hydrogen and oxygen. In this case, the external species is in particular water vapor. Here, the water vapor content in hydrogen is in equilibrium with the gas pressure of hydrogen on the suction side.

  In an advantageous configuration, in the transport step 304, hydrogen is transported to the pressure side at a set pressure and / or set temperature and / or set purity. It is possible to set how much pressure is generated on the pressure side according to the electric potential. In order to control the temperature, heating elements and / or cooling elements may be arranged on the pressure side.

  In an advantageous configuration, a DC voltage is applied to each electrode in the transport step 304.

  In an advantageous configuration, in the transport step 304, ions are transported quasi-isothermally through the membrane. Almost no temperature change occurs between the suction side and the pressure side due to the electric potential. This eliminates energy consumption associated only with undesired temperature changes in mechanical compression.

  In an advantageous configuration, the preparation method 300 further comprises an accumulation step. In the accumulation step, hydrogen is accumulated in the pressure accumulator on the pressure side.

  The illustrated embodiment is only selected as an example. The various embodiments can be arbitrarily combined, either completely or in connection with individual features. One embodiment can also be supplemented by the features of another embodiment.

  It should be noted that the steps of the method of the present invention can be performed iteratively or in an order different from that described above.

  In the description of the embodiment, when the first feature and the second feature are connected by “and / or”, this means that the embodiment has only the first feature or only the second feature. Or means that both the first feature and the second feature may be included.

  100 hydrogen preparation device, 102 hydrogen, 104 electrochemical compressor (electrochemical cell), 106 generator (electrolysis layer stack), 108 membrane, 110, 112 electrode, 114 ion, 116 suction side, 118 pressure side, 120 external species, 200 electrolysis system, 202 electrical energy, 204 water, 206 oxygen, 208 pressure accumulator, 300 hydrogen preparation method, 302 generation step, 304 transport step

Claims (12)

A method (300) for preparing hydrogen (102) comprising:
The method (300) comprises:
Producing (302) hydrogen (102) that can be produced on the suction side (116) of the electrochemical compressor (104) by involving external species (120);
In order to increase the hydrogen partial pressure on the pressure side (118) of the compressor (104) and to retain the external species (120) on the suction side (116) of the compressor (104), the compressor (104 ) Using the electrical potential between the first electrode (110) on the suction side (116) and the second electrode (112) on the pressure side (118) of the compressor (104), Transporting the hydrogen (102) ions (114) through the membrane (108) of the compressor (104) (304). In the generating step (302), by using electric energy to decompose water (204) into hydrogen (102) and oxygen (206), the external species (120) is in particular water vapor (120), Producing the hydrogen (102),
The method (300) of claim 1. In the transporting step (304), transporting the hydrogen (102) to the pressure side (118) at a set pressure and / or set temperature and / or set purity;
The method (300) of claim 1 or 2. In the transporting step (304), a predetermined DC voltage (202) is applied to the electrodes (110, 112).
Method (300) according to any one of claims 1 to 3 In the transporting step (304), the ions (114) are transported quasi-isothermally through the membrane (108).
The method (300) according to any one of the preceding claims. Further comprising accumulating the hydrogen (102) in the pressure accumulator (208) on the pressure side (118);
The method (300) of any one of claims 1-5. A hydrogen (102) preparation device (100) comprising:
The preparation device (100) comprises an electrochemical compressor (104) comprising a membrane (108) and a first electrode (110) on the suction side (116) and a second electrode (112) on the pressure side (118). And a generator (106) capable of generating hydrogen (102) on the suction side (116) of the compressor by involving external species (120),
In the compressor (104), to increase the hydrogen partial pressure on the pressure side (118) and to retain the external species (120) on the suction side (116), the first electrode (110) An electrical potential is formed between the second electrode (112) and ions (114) of the hydrogen (102) from the suction side (116) of the compressor (104) to the compressor (104). ) To the pressure side (118) of the device (100). The generator (106) uses electrical energy (202) to decompose water (204) into hydrogen (102) and oxygen (206) so that the external species (120) is in particular water vapor (120). An electrolyzer (106) configured to:
The apparatus (100) of claim 7. The compressor (104) includes at least one other membrane (108) having another first electrode (110) on the suction side and another second electrode (112) on the pressure side,
The another membrane (108) and the membrane (108) are arranged one after the other, and the hydrogen partial pressure is gradually increased from the suction side (116) toward the pressure side (118). Configured to enhance,
Apparatus (100) according to claim 7 or 8. The membrane (108) is configured as a polymer electrolyte membrane (108),
Device (100) according to any one of claims 7 to 9. The membrane (108) has a discharge portion for discharging the external species (120).
Device (100) according to any one of claims 7 to 10. The apparatus further comprises a pressure accumulator (208) for accumulating the hydrogen (102) on the pressure side (118).
Device (100) according to any one of claims 7 to 11.

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